1. Field of the Invention
The invention relates to an improved hermetic enclosure for either single or multiple electronic components, including integrated circuit chips, and which includes conduction runs within the enclosure leading to terminals on the exterior of the enclosure. More particularly, the invention relates to a novel hermetic enclosure and to a novel method of making such an enclosure which avoids exposing the components to temperatures that are too high for safety.
2. Description of the Prior Art
Electronics packaging, and more particularly the packaging of single or multiple integrated circuit chips has posed a challenge to the electronic industry. The packaging has had to meet divergent standards. A critical distinction is the imperviousness of the package to moisture penetration. Conventional plastic packages (epoxy, etc.) have been rejected for many critical applications because of their penetrability by moisture. A high quality hermetic package for semiconductor components while not usually maintained in a vacuum, is usually filled with a passivating, inert gas, typically Nitrogen. The passivating property remains high so long as moisture and oxygen levels remain appropriately low. Packaging meeting these requirements has included metal, glass, and ceramics, including alumina, and more recently beryllia. The ceramic materials are formed by a high temperature sintering process (1400.degree. C.), which increases the density of the material over the "green" hot pressed form, and reduces the porosity to the point where it becomes an excellent hermetic, low leakage material.
The packages using ceramic material must usually be assembled at high temperatures from several parts and the construction must also provide for electrical connections passing through the package between enclosed components and external terminals. The processing of the conduction runs is also at a high temperature, well above temperatures which are safe for semiconductors. The lowest of these temperatures is 400.degree.-500.degree. C. for a resinous thick film process, and somewhat higher for a conventional frit process in which a "moly manganese" layer is mixed with glass, and the glass is fused to form a binder of the conductive material to the substrate. The sealing of the package either to other ceramic parts or over thick film processed conduction runs also requires an elevated temperature typically that of a low temperature (.about.500.degree. C.) glass seal. This temperature is also too high a temperature for safe exposure to semiconductor components.
A need has also developed for a transparent package for either optical inspection or for optical signalling to the enclosed components. Optical coupling is capable of very large bandwidths, and avoids some of the problems present in other high bandwidth connections.